Polyvinyl chloride resins containing a trialkyl lead cyanide as a stabilizer



United States Patent 3,262,909 POLYVINYL CHLORIDE RESINE CONTAHNING ATRIALKYL LEAD CYANIDE AS A STABHLIZER Richard D. Gorsich, Baton Rouge,La, assignor to Ethyl Corporation, New York, N.Y., a corporation ofVirginia No Drawing. Filed May 31, 1963, Ser. No. 284,348 9 Claims. (Cl.26045.75)

This invention concerns thermal stabilization of haloethylene polymers.More particularly, it relates to new compositions based on haloethylenepolymers, in particular vinyl chloride resins, having improved thermalstability over the prior known compositions.

It is known that haloethylene polymers such as polyvinyl chloride andthe copolymers of vinyl chloride and vinylidene chloride undergoappreciable degradation and darkening when heated during thermalfabrication operations and when the fabricated articles are exposed forprolonged periods to elevated temperatures. During the formation ofresins into plastic sheets, rigid bodies and the like, the materials areworked at high temperatures. High temperature working of the materialfacilitates the forming operation and decreases the time during whichhot work is needed, increasing the capacity of the equipment. Howeversuch high temperature working results in the rapid deterioration of theresin. This is evidenced by a yellowing and then a progressive darkeningof the material. The initial color transparent stock turning, in stages,yellow, tan, and then brown, black and opaque. Such thermal sensitivityhas seriously limited the applications in which these haloethylenepolymers may be employed. One of the common means for alleviating thisdegradation has been to employ certain additives as heat stabilizers inthe polymer formations. However, the requirements of a suitable heatstabilizer are manifold and varied. To be suitable for commercial use,the stabilizers must be compatible in the resin, must have a minimum ofplateout during milling, and must retard the deteriorative effects ofheat and light. The most desirable resins are those that are initiallyclear and transparent and retain this condition for the longest periodof time. The onset of a distinct yellow cast to a transparent stabilizedresin is an indication of the limit of usefulness of the resin.

Several lead compounds, e.g. lead stearate and lead phthalate, arerecognized by the art to have suitable stabilization properties, howeverthe lead compounds in general are known to have drawbacks particularlybecause of their possible reactivity with the resin, plastieizers, andother compound ingredients. Also the commercial lead stabilized are ingeneral incompatible with the resin and results in opaque material. Dueto these disadvantages particularly the opacity of the resins thepresent use of lead compounds is restricted to electrical insulation andthe like. There is however a need in the art for lead compounds whichare compatible with the resin and which results in resins that are clearand transparent due to the fact that lead compounds in general arecheaper and more readily available than other compounds presently incommercial use.

Accordingly it is the chief object of this invention to provide novelstabilized halogen containing resins, particularly vinyl chloride resinsstabilized with particular lead compounds.

It is a further object of this invention to provide vinyl chlorideresins containing certain lead compounds which are clear and transparentand which retain this condition for extended periods of time.

It is a further object of this invention to provide a process for theproduction of vinyl chloride resins having improved stability.

3,252,909 Patented July 26, 1966 Other objects and advantages willbecome more apparent from the following description.

The above and related objects are accomplished by a vinyl chloride resinstabilized against discoloration by having incorporated therein atrialkyl lead cyanide in an amount sufficient to stabilize the resinagainst discoloration said trialkyl lead cyanide having from 1 to about5 carbon atoms in each alkyl group and more preferably from 1 to about 3carbon atoms. Trimethyllead cyanide is particularly preferred due to theexcellent results achieved therewith. Alkyl radicals having a greaternumber of carbon atoms may, of course, be employed however the alkylradicals outside the aforementioned ranges merely increase the costwithout incurring any additional benefits.

Particularly preferred resins are polyvinyl chloride and vinyl chloridecopolymers.

The lead compounds of this invention show stabilizing effectiveness inany concentration and are particularly effective when used in an amountranging from about 0.01 to 10 percent, and more preferably from 1.5 to 5percent, by weight based on the weight of the resin or polymer. Whenmore than 10 percent is used, the stabilizers become economicallyunattractive and no additional benefits accrue.

In addition to imparting thermal stability to the resin andcompatibility with the resin these compounds possess the additionaladvantages in that they are colorless and odorless. Articles preparedfrom these compounds are more merchantable than those prepared from manyof the known compositions due to their absence of odor.

The stabilizers of this invention may be employed with other commonadditives used in haloethylene polymer formulations without any adverseeffect resulting therefrom. Typical of such additives are lightstabilizers, fillers, pigments and dyes.

These stabilizers may be incorporated into the polymer formulations byany known blending technique, such as mil-ling and dry blending. It ispreferred that the lead compound be in a finely comminuted state forblending purposes to achieve uniform dispersion of the salt through theformulation more easily.

By way of example and comparison several sample compositions wereprepared. A formulation of 1 part by weight of each particularstabilizer and 50 parts by weight of di-Z-ethy-l-hexyl phthalate (DOP)were handmixed in 250 mil glass beakers. 50 parts of polyvinyl chloridewere than stirred into each of the above described formulations and theresulting plastisols were deaerated for 17 hours in a vacuum desiccatorat room temperature. The formulations were then poured into a six inchby three inch by one-sixteenth inch chase enclosed between 2 polished,chrome-plated steel sheets, weighted with a 3,550 gram load and fusedfor 30 minutes at 177 C. in a circulating air oven. The molded sheetswere examined visibly for compatibility and stability. The results arelisted in the following table.

The above results demonstrate that the trimethyllead cyanide of thepresent invention initially produces a transparent clear resin Whereasthe lead phthalate which is now in commercial use produces an Opaqueresin which shows slight yellowing. Also it is noted that thetrimethyllead cyanide shows qualities which are at least equal to alkyltin mercaptide and the Ba-Cd-Zn soap also Widely used as commercialstabilizers.

The molded sheets described above were next evaluated for thermalstability by cutting them into numerous threequarter inch bythree-quarter inch squares, placing these samples on aluminum foilstrips in a 175 C. circulating oven and removing sets of samples every15 minutes for 2 hours. These samples were then mounted on display cardsfor direct visual comparison. The results are summarized in the tablebelow.

4 The stabilizers of the present invention are also effectivestabilizers for organosols and plastisols. Plasticizers commonly used inplasticized resins, organosols and plastisols include esters of thefollowing acids: phthalic acid, adipic acid, subacic acid, azelaic acid,ciyric acid, aconitic acid, tricarboxylic acid, maleic acid, fumaricacid, succinic acid, phosphoric acid and mercapto acids likethioglycolic acids and the like; esters of dihydric and polyhydricalcohol, such as glycol, glycerol, pentaerythritol, sorbitol, and thelike; esters of thioglycols and other sulfur-containing derivatives;amino alcohol derivatives; ester amides, sulfonamides, and other amides,chlorinated plasticizers and carbonic acid derivatives derived fromphosgene.

The stabilizers of this invention are useful with halogen containingresins having incorporated therein other stabilizers and otherplasticizers.

TABLE II.HEATING CONDUCTED AT 175 C.

Run Stabilizer Hour Hour Hour I Alkyl Tin Mereaptide" Transparent, whiteTransparent, white. Transparent, brown tinge.

Lead Phthalate Opaque, slight yellow tin Opaque, sllght yellow tinge..."Opaque, yellow tinge. Ba-Cd-Zn Soap Transparent, white Transparent,yellow Transparent, tan. I Trimethyl Lead Gyai do Transparent, browntinge.

Triethyl Lead Stearate light brown.

11 e. Triethyl Lead Glycollate Phenyl Urethane. bubbles, tan.

Opaque,filled with large bubbles, Opaque, filled with large bub- Opaque,filled with small bubbles,

tan.

Transparent, filled with small Opaque, filled with large bubbles, brown.bles, dark brown. Opaque, filled with small bub- Opaque, filled withsmall bubbles, tan. bles, brown.

Transparent, filled with small bubbles, dark brown.

Transparent, filled with small bubbles, black.

It is seen from the foregoing table that trimethyllead cyanide shows atleast equivalent stability with alkyl tin mercaptide, superior thermalstability to the barium-cadmium-zinc soap and highly superior qualitiesparticularly in clarity to the lead phthalate.

Similar results are achieved when the above runs are repeated usingtriethyl lead cyanide, tripropyl lead cyanide, tripentyl lead cyanide,trioctyl lead cyanide, methylethyl-isopropyl lead cyanide. The runs arealso repeated using the diethyl ester of adipic acid and the diisopropylester of azelaic acid as plasticizers.

When the above runs are repeated using the co-polymers of vinyl chlorideand vinylidene chloride and vinyl chloride and vinyl acetate similarcompatibility and thermal stability is observed.

Generally speaking, the halogen-containing resins, which are renderedheat and light resistant by the stabilizers of this invention, arepolymers of vinyl chloride and vinyl resins containing vinyl chlorideunits in the structure, such as copolymers of vinyl chloride with vinylesters of aliphatic carboxylic acids, particularly vinyl acetate,copolymers of vinyl chloride with esters, nitriles and amides ofunsaturated carboxylic acids, e.g., of acrylic and methlacrylic acids,copolymers of vinyl chloride with diene compounds and with unsaturateddicarboxylic acids or in anhydrides, such as copolymers of vinylchloride with diethyl maleate, diethyl fumarate, or maleic anhydride,after, chlorinated polymers and copolymers of vinyl chloride, polymersof vinylidene chloride and copolymers of the same with vinyl chlorideand other polymerizable compounds; polymers of vinyl ehloroacetate anddichlorodivinyl ether; chlorinated polymers of vinyl acetate,chlorinated polymeric esters of acrylic and acrylic alphasubstitutedacrylic acids; polymers of chlorinated styrenes, for instance,dichlorostyrene, chlorinated rubber, chlorinated polymers of ethylene,polymers and after-chlorinated polymers of chlorobutadiene, and theircopolymers with vinyl chloride; rubber hydrochloride and chlorinatedrubber hydrochloride, and mixtures of the polymers recited herein witheach other polymerizable compound.

While the invention has been described with particular reference tospecific embodiments, it is to be understood that it is not limitedthereto but is to be construed broadly and is to be restricted solely bythe scope of the appended claims.

What I claim is as follows:

1. A vinyl chloride resin stabilized against discoloration by havingincorporated therein a trialkyl lead cyanide in an amount suificient tostabilize the resin against discoloration said trialkyl lead cyanidehaving from 1 to about 5 carbon atoms in each alkyl group.

2. A composition as defined in claim 1 in which the resin is a vinylchloride copolymer.

3. A composition as defined in claim 1 in which the resin is polyvinylchloride.

4. A composition as defined by claim 1 wherein the concentration oftrialkyl lead cyanide is from about 0.01 percent to about 10 percentbased on the total weight of the resin.

5. A composition as defined by claim 1 wherein the concentration oftrialkyl lead cyanide is from about 1.5 to about 5 percent based on thetotal weight of the resin.

6. A composition as defined by claim 1 wherein the concentration oftrialkyl lead cyanide is about 2 percent based on the total Weight ofthe resin.

7. A composition as defined by claim 1 wherein the trialkyl lead cyanideis trimethyl lead cyanide.

8. A composition of matter comprising polyvinyl chloride resin havingincorporated therein from about 0.01 to about 10 percent of trimethyllead cyanide.

9. A composition of matter comprising polyvinyl chloride resin havingincorporated therein from about 1.5 to 5 percent of trimethyl leadcyanide based on the total weight of the resin.

References Cited by the Examiner FOREIGN PATENTS 1,064,236 8/1959Germany.

LEON J. BERCOVITZ, Prima/y Examiner.

G. w. RAUCHFUSS, .TR., Assistant Examiner.

1. A VINYL CHLORIDE RESIN STABILIZED AGAINST DISCOLORATION BY HAVINGINCORPORATED THEREIN A TRIALKYL LEAD CYANIDE IN AN AMOUNT SUFFICIENT TOSTABILIZED THE RESIN AGAINST DISCOLORATION SAID TRIALKYL LEAD CYANIDEHAVING FROM 1 TO ABOUR 5 CARBON ATOMS IN EACH ALKYL GROUP.